[GIS] ArcGIS Javascript API – carrying out multiple query tasks

Question

I have carried out a QueryTask on a map service that returns a polygon when I input a postcode. Within the same service there is an additional layer that allows the user to query a local authority name on. I would like to carry out a querytask on this layer at the same time so that the map returns a polygon relating to the postcode input and also tells me what local authority it is contained within. I will ultimately show the local authority in a separate widget.
Can anyone help please?

Answer 1

Correct me if I'm wrong, but it sounds like the layer with the local authority data is separate from the layer with the post code.

You'll need a second QueryTask for the layer with the local authority data. When the first QueryTask returns the polygon boundary of the post code, pass that polygon geometry into a Query.geometry parameter, and use the new query parameters in the second QueryTask. I've provided a little sample code below.

var postCodeQueryTask = new QueryTask(" /* insert your map service layer url for the post code */ ");
var localAuthQueryTask = new QueryTask(" /* insert map service url for the local authority data */ ");
var postParameters = new Query();

// do stuff to query the post code

// execute the queryTask for the post code
postCodeQueryTask.execute(postParameters, function (featureSet) {
  // do stuff with post code geometry

  // use the geometry to load the local authority data.
  var localAuthParam = new Query();
  localAuthParam.geometry = featureSet.features[0].geometry;
  // do other things to set up your new query

  localAuthQueryTask.execute(localAuthParam, function (localAuthFS) {
    // your featureSet with the local authority data is here.
  });

});